نتایج جستجو برای: chemical shielding

تعداد نتایج: 386370  

2005
Z. L. Wang Q. Wang H. J. Li J. J. Li P. Xu Q. Luo A. Z. Jin H. F. Yang C. Z. Gu

High aspect ratio diamond nanocone arrays are formed on freestanding diamond film by means of focused ion beam (FIB) milling technology and hot-filament chemical vapor deposition (HFCVD) method. The structure and phase purity of an individual diamond nanocone are characterized by scanning electron microscopy (SEM) and micro-Raman spectroscopy. The result indicates that the diamond cones with hi...

Journal: :Chemical science 2017
Lars A Bratholm Jan H Jensen

The accurate prediction of protein chemical shifts using a quantum mechanics (QM)-based method has been the subject of intense research for more than 20 years but so far empirical methods for chemical shift prediction have proven more accurate. In this paper we show that a QM-based predictor of a protein backbone and CB chemical shifts (ProCS15, PeerJ, 2016, 3, e1344) is of comparable accuracy ...

Journal: :Dalton transactions 2014
Nicola Salvi Julien Frey Diego Carnevale Michael Grätzel Geoffrey Bodenhausen

The ruthenium-containing sensitizing dye N719 grafted on TiO2 nanoparticles was investigated by solid-state NMR. The carbon resonances are assigned by means of (13)C cross-polarized dipolar dephasing experiments. DFT calculations of the carbon magnetic shielding tensors accurately describe the changes in chemical shifts observed upon grafting onto a titania surface via one or two carboxylic fun...

Journal: :Journal of magnetic resonance 2005
Young-Sik Kye Xingang Zhao Gerard S Harbison

We have derived analytical expressions for determining the orientation of high-symmetry single crystals from line-crossings in a single rotation plot. We demonstrate the utility of the method using the strontium-87 resonance in strontium nitrate. Employing our new method, which we call orientation of single crystals using linear approximations to NMR transits (OSCULANT), in combination with fou...

Journal: :Physical chemistry chemical physics : PCCP 2011
Leonardus W Jenneskens Remco W A Havenith Alessandro Soncini Patrick W Fowler

Direct evaluation of the induced π current density in [5]paracyclophane (1) shows that, despite the significant non-planarity (α = 23.2°) enforced by the pentamethylene bridge, there is only a modest (ca. 17%) reduction in the π ring current, justifying the use of shielding-cone arguments for the assignment of (1)H NMR chemical shifts of 1 and the claim that the non-planar benzene ring in 1 ret...

2002
A. B. Reimann J. Fajans

The response of collisionless plasmas to an applied potential can differ from classic Debye shielding, and when the potential is rapidly applied ~‘‘instantaneous shielding’’!, the shielding can differ from when it is slowly applied ~‘‘adiabatic shielding’’!. Experiments demonstrate that when a test potential well is applied to a one-dimensional pure-electron plasma, instantaneous and adiabatic ...

Magnesium oxide nanoclusters have attracted much attention due to their potential applications to catalysis and novel optoelectronic materials. In the present study, we have studied the electronic and magnetic properties of the stoichiometric magnesium oxide nanoclusters (MgO)n  for n = 2-20. Although the binding energy increases with the size of the cluster, it  re...

Journal: :The Journal of organic chemistry 2015
Ellie L Fought Shreyosree Chatterjee Theresa L Windus Jason S Chen

2,2,6,6-Tetramethylpiperidinyl-masked 1,2-diols exhibited stereochemistry-dependent hydroxyl proton chemical shifts: ca. 7 ppm for the syn diastereomer and ca. 2 ppm for the anti diastereomer. A computational search for low energy geometries revealed that the syn isomer favors a six-membered ring hydrogen bond to nitrogen and the anti isomer favors a five-membered ring hydrogen bond to oxygen. ...

Journal: :Physical chemistry chemical physics : PCCP 2011
Jérôme Cuny Kateryna Sykina Bruno Fontaine Laurent Le Pollès Chris J Pickard Régis Gautier

Solid-state (95)Mo nuclear magnetic resonance (NMR) properties of molybdenum hexacarbonyl have been computed using density functional theory (DFT) based methods. Both quadrupolar coupling and chemical shift parameters were evaluated and compared with parameters of high precision determined using single-crystal (95)Mo NMR experiments. Within a molecular approach, the effects of major computation...

Journal: :Journal of biomolecular NMR 1994
H Le E Oldfield

An empirical correlation between the peptide 15N chemical shift, delta 15Ni, and the backbone torsion angles phi i, psi i-1 is reported. By using two-dimensional shielding surfaces delta (phi i, psi i-1), it is possible in many cases to make reasonably accurate predictions of 15N chemical shifts for a given structure. On average, the rms error between experiment and prediction is about 3.5 ppm....

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